Officials urged caution and warned of black ice as frigid temperatures approach, after a morning of flooding on Long Island’s south shore. NewsdayTV’s Cecilia Dowd reports.

This story was reported by Robert Brodsky, Joan Gralla, Brianne Ledda, Lorena Mongelli, Alfonso Castillo and Joe Werkmeister. It was written by Brodsky.

Long Island was bracing for a major blast of arctic, subfreezing temperatures Friday overnight into Saturday — the second leg of a double-barreled storm that already brought widespread flooding, power outages and transportation delays during the busy holiday season.

Just as Long Islanders, from western Nassau County to Suffolk County's East End, began to clean up from the Thursday night's ferocious storm, an early Christmas present arrived on their icy cold doorsteps.

Temperatures plummeted more than 30 degrees into the midteens early Friday evening with wind gusts of up to 55 mph, according to the National Weather Service in Upton.

And it was only expected to get colder overnight, forecasters said, with wind chills potentially reaching 15 degrees below zero, and a dusting of snow expected in some areas.

Another concern — any standing water from the earlier storm could quickly freeze over into the black ice, creating for treacherous road conditions.

"There will be a significant amount of ice on the roads even though we're out salting. It'll be a dangerous condition," Nassau County Executive Bruce Blakeman said during a storm briefing Friday in Bethpage. " … Do not go out on the roads unless you have to. Tomorrow will be a much better day to go shopping."

Nassau is opening warming centers Saturday at Wantagh and Cantiague parks from 8 a.m. to 6 p.m. and 24-hours-per day at Mitchel Field in Garden City. Nassau police will encourage homeless residents to come inside to one of the warming centers.

Meteorologist Bill Korbel explains what a "Bomb Cyclone" is, and if it is heading in our direction Credit: NewsdayTV

The winter blast Friday followed some of the worst flooding in a decade on Long Island, from waterlogged basements in East Rockaway — where one resident needed to be evacuated by police — to widespread flooding in the Town of Southampton that brought back memories of the worst storm in recent memory.

“This is probably the most amount of flooding that we’ve seen since Sandy,” said Ryan Murphy, Southampton's public safety and emergency management administrator, noting that the storm was boosted by a new moon, similar to the 2012 superstorm.

Across Long Island, the damage was widespread.

Nassau police responded to more than 100 calls for individuals trapped in their vehicles and nearly three dozen crashes, said Commissioner Patrick Ryder. Suffolk police did not see a rise in 911 calls during the storm.

In Island Park, the blaring sound of car alarms awoke Isabella Franzese, 53, at the Radcliffe Road home she and her husband moved into last week. Moments later, a man on a kayak floated by, checking on neighbors.

“I’m ready to move to Arizona right now,” she said, eying what she described as "a lot of property damage" in her area.

Southold Town Supervisor Scott Russell said the storm left a “mess” and a shelter was being set up for displaced residents.

“We have some wires across the road," Russell said. "We have a couple of poles across the road. Also a lot of floods. A lot of puddling. It’s a mess out there."

Nicole Alloway, 50, of Southold, concurred with that assessment as she waited for the electricity to come back on in her Bayview Peninsula neighborhood.

"The lot next to our house is completely covered with water and the waves on the Peconic Bay are reaching to the top of my mom’s flagpole," she said. "It was a hell of a storm overnight."

PSEG Long Island outages peaked at nearly 28,000 customers without power, the utility said. On Friday night, more than 4,500 Long Islanders, largely in the towns of Southold, Brookhaven, Huntington, and Oyster Bay, were still without power, according to the utility's outage map.

The storm also wreaked havoc on commuters, from the roads and seas to the rails and skies.

Nearly 700 flights into and out of New York airports were delayed while more than 550 others were canceled.

The Long Island Rail Road suspended service on its low-lying Long Beach branch because of flooding.

The Nassau Inter-County Express, or NICE Bus, was cross-honoring LIRR fares on its N15 line between Rockville Centre and Long Beach but advised customers to expect delays and detours because of "icy dangerous road conditions."

The flooding caused the temporary closures of parts of the Meadowbrook and Wantagh State parkways — they later reopened — and left much of Jones Beach State Park underwater, including the boardwalk.

“At Gilgo State Park, the water is up to the dunes," said George Gorman, regional director of the New York Office of Parks, Recreation and Historic Preservation. "At Robert Moses State Park, the entire beachfront is covered with water except for the far end of Field 2."

The Fire Island ferry canceled evening service Friday, with Cliff Clark, chief executive of the South Ferry that runs between Shelter Island and North Haven, noting that water levels were "the highest we’ve had since Sandy."

But there is a touch of good news.

Both Saturday’s Christmas Eve Day, with an official daytime high of 21 degrees, and Sunday’s Christmas, with a daytime high of 27, will be sunny and dry.

Credit: Newsday

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Credit: Newsday

Emergency plane landing on beach ... Manufacturing jobs coming to LI ... Sci-Fi Renaissance Stony Brook protesters cleared ... Giraffe death response ... Emergency plane landing on beach  ... What's Up on LI

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